1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to software-controlled communications, and more particularly, to simultaneously supporting a 900 MHz cordless phone and a handset transceiver via software.
2. Description of the Prior Art
With the development of a communication technology, various cordless phones and handset transceivers have been developed. For example, FIG. 1 illustrates the construction of a conventional cordless phone.
The cordless phone 100 may include a radio frequency (RF) transceiver 110 having an antenna 107 for transmitting/receiving an RF signal; a signal search unit 140 for searching for a specific signal; a frequency modulation (FM) modulator 165 and an FM demodulator 115 for performing FM modulation and demodulation, respectively; a minimal shift keying (MSK) modulator 160 and an MSK demodulator 135 for respectively performing MSK modulation and demodulation for data communication; and circuits such as a compressor 175, an extender 125, a pre-emphasis unit 170, and a de-emphasis unit 120 for voice communication. The cordless phone 100 may also include a microphone 180, a speaker 130, a display 150, and a key 155 for a voice input/output and user interface, and a controller 145 for controlling the aforementioned constituent elements. A cordless phone base station 105 can be combined with or separated from the cordless phone 100.
First, a case where the RF transceiver 110 receives the RF signal from the cordless phone base station 105 through an antenna 107 will be described.
The controller 145 controls a local oscillator included in the RF transceiver 110 to change a reception channel while monitoring whether a signal exists in each channel. At this time, the signal search unit 140 monitors a signal level of a corresponding channel, and if it is determined that a signal exists, the FM demodulator 115 demodulates the signal. An output signal of the FM demodulator 115 is MSK-demodulated through the MSK demodulator 135 to determine whether a predetermined data frame header exists.
If it is determined that the predetermined data frame header exists, the controller 145 analyzes the MSK-demodulated signal, and controls a call depending on the content of a message received from the cordless phone base station 105. For example, if received data represents “ring on,” a phone bell rings. When the line is busy and no message data exists, the signal demodulated by the FM demodulator 115 passes through the de-emphasis unit 120 and the extender 125, thereby allowing the voice call through the speaker 130.
In general, the controller 145 employs a microcomputer having firmware installed therein for control.
Now, a case where a call is made with the cordless phone 100 will be described.
First, the user presses a key 155 such as a “call” button of the cordless phone 100 to initiate the operation. At this time, the controller 145 uses a set channel or selects a channel using a method of searching for a channel having the least crosstalk, and controls the local oscillator in the RF transceiver 110 to fix the channel. The controller 145 generates a message representing “call,” and the MSK modulation is performed by the MSK modulator 160. The MSK-modulated signal is FM-modulated by the FM modulator 165. The FM-modulated signal is carried in a channel selected by the RF transceiver 110; that is, the signal is transmitted to the cordless phone base station 105 through the antenna 107.
If the call is permitted by the cordless phone base station 105 and a dial tone sounds, the user can make the call by pressing numeral buttons of the cordless phone 100. At this time, data of the pressed button is transmitted to the cordless phone base station 105, and it is converted by the cordless phone base station 105 using a dual-tone-multi-frequency (DTMF) method, and the call is made.
On the other hand, the handset transceiver generally operates in a half-duplex mode where one channel is shared. In this method, a voice signal is FM/AM-modulated and carried in the channel only when a receiver button is pressed, while a channel signal is FM/AM-demodulated to reproduce voice when the receiver button is not pressed.
In the cordless phone as described above, all operations are performed by a hardware circuit, and even the firmware installed in the controller 145 that controls the system is designed to be limited only to the corresponding hardware.
Accordingly, different kinds of hardware and firmware are used by respective manufacturing companies, thereby causing many limitations in extensibility, compatibility, and reuse of appliances. These limitations are also the same as those of the handset transceiver. Although a plurality of handset transceivers of respective manufacturing companies can communicate using a frequency modulation and demodulation method, these limitations are caused by sharing (crosstalk) of a communication channel, rather than by the extensibility, compatibility and reuse of the appliances.
That is, a conventional method performs most signal controls and control processes by hardware, and thus supports only the frequency band and data communication protocol considered when designing the hardware. Accordingly, it is difficult to provide compatibility between products, or to support a new frequency band, new modulation/demodulation method, or new communication protocol. In order to solve this, a method is required whereby functions implemented by hardware are minimized and most functions are processed by software.
Such a software communication apparatus does not only facilitate the provision of a communication function of the handset transceiver or cordless phone in a computing appliance such as a personal computer (PC), but it can also be used for the development of other communication systems since it heightens the reusability of developed software, thereby greatly reducing the period for developing the system. Accordingly, a software controlled communication method is required.